HV (high voltage) screening is practiced for avoiding shipment of semiconductor devices having low reliability. For example, there is a screening method which applies a voltage that is higher than a voltage normally used in operation to gate electrodes of output MOS transistors and intentionally breaks such output MOS transistors which have low-quality gate oxide film so as to eliminate low-quality semiconductor devices before the devices are shipped. Thus, the screening method also includes a test for checking whether a semiconductor device after application of high voltage can normally function or not, a test for checking the presence or absence of leakage current, and other tests to determine the semiconductor device as a good product or a faulty product.
As described above, the HV screening requires the application of high voltage to gate electrodes of output MOS transistors. In the case of output MOS transistors being provided with gate protection diodes, however, the gate protection diodes clamp voltage between the gate and source electrodes and the high voltage may not be applied to the gate electrodes of the output MOS transistors. For solving this problem, switch elements are connected to the gate protection diodes and the high voltage is applied after the switch elements are turned off.